The present invention relates to a novel push-button switch or, more particularly, to a push-button switch with which consecutive signals of switching on and off are spontaneously obtained by a single action of pushing the button.
Many electric and electronic instruments and appliances are provided with one or more of push-button switches either as isolated ones or as a panel of key-board switches. A variety of structures and principles are utilized for these push-button switches according to need. One of typical structures of such push-button switches is composed of a base plate having a pair of contact points fixedly provided thereon and a dome-like covering facing the contact points made of a diaphragm of a flexible and resilient material having a movable contact member on the inward surface thereof at the top portion of the dome so as that the electric circuit between the fixed contact points on the base plate is closed when the contact member is downwardly depressed with a finger tip or the like from above the top portion of the dome to come into contact with the fixed contact points. When the pushing force on the top portion of the dome is removed, the contact member comes apart from the contact points by virtue of the resilience of the diaphragm material so as to open the electric circuit between the contact points on the base plate.
Push-button switches of such a type are widely employed owing to the simplicity of their structure but they are defective in some aspects including the undesirable transient disturbances of the phenomena of so-called chattering or bouncing. Therefore there have been made various attempts to eliminate the undesirable phenomena from the push-button switches of the type. For example, chattering or bouncing can be reduced when the contact member is made of an electroconductive rubbery material. Unfortunately, none of the hitherto undertaken attempts is perfect so that many instruments with such a push-button switch, e.g. computers, electronic calculators, electric typewriters, cash registers and the like, in which high reliableness in switching is of utmost importance, cannot be free from the problem of erroneous operation by the irregularities in switching caused by the chattering or bouncing of the electric contact, especially, in the moment of releasing of the pushing force on the push-button by lifting the finger tip depending on the very delicate but unreliable movement thereof although the contacting movement of the contact member is more reliable than in the releasing of the pushing force.